• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.3
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• pp.105-110
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• 2015

The fiber-reinforced endodontic posts were prepared using a photocurable resin and a glass fiber. The mechanical property of the posts increased with increasing density of glass fiber and the micro-pores in the post were removed by a vacuum impregnation process. To improve the interfacial adhesion between glass fiber and polymer, silane coupling agent was used. The surface treatment of glass fiber increased the surface wettability of resing on glass fiber and increased the adhesion property with resin, consequently improved the mechanical property of posts.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.117-123
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• 2014

Cu through-vias, which can be used as thermal vias or vertical interconnects, were formed using bottom-up electrodeposition filling as well as top-down electrodeposition filling into open via-holes and their microstructures were observed. Solid Cu through-vias without voids could be successfully formed by bottom-up filling as well as top-down filling with direct-current electrodeposition. While chemical-mechanical polishing (CMP) to remove the overplated Cu layer was needed on both top and bottom surfaces of the specimen processed by top-down filling method, the bottomup process has an advantage that such CMP was necessary only on the top surface of the sample.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.130-135
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• 1999

The enhanced slag fineness and the batch water of low water-to-cement ratio(W/C) were employed in order to improve the early strength of blast-furnace slag blended cement at low temperature. A grinding aid was used to grind the blast-furnace slag into the fineness of 6,280$\textrm{cm}^2$/g (Blaine), and this fine slag was then homogeneously mixed with the ordinary Portland cement to produce the blast-furnace slag blended cement containing 40% slag by weight composition. On the other hand, the batch water could be reduced from W/C=0.50 (KS L 5105) to W/C=0.33 through a commercial, naphthalene type superplasticizer. Through the method mentioned above, the early strength of the blast-furnace slag blended cement at low temperature could be enhanced even somewhat higher than the Portland cement strength. And the microsturcture of the cement was studied by both the pore structure analysis and the A.C. impedance measurement.

• Electrical & Electronic Materials
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• v.9 no.6
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• pp.605-615
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• 1996

In this paper, the effect of alkaline oxide addition such as Li$_{2}$O and Na$_{2}$O on the microstructure and humidity sensitivity of V$_{2}$O$_{5}$(2 mol%)-doped TiO$_{2}$(98 mol%) was investigated as a function of amount (0, 1, 2, 5, 10 mol%) of Li$_{2}$O and Na$_{2}$O additives. The pores in the alkaline free sample were distributed mostly in the range between 0.16 and 1.0.mu.m in diameter and its porosity was 23.29%. Li$_{2}$O caused grain overgrowth and reduced the porosity with a narrow distribution of the pore size, leading to poor humidity sensitivity. Na$_{2}$O helped to enlarge the distribution of the pore size through the formation of small soluble phases. The pore sizes of the sample containing Na$_{2}$O 2mol% were distributed mostly in the range between 1.0 and 2.5.mu.m in diameter and its porosity and intrusion volume of mercury were 31.13 % and 0.1155 mL/g respectively, which consequently improved the humidity sensing characteristics such as the sensitivity and temperature-stability. Especially, the addition of 2mol% of Na$_{2}$O improved the humidity-sensing characteristics such as sensitivity and linearity in the whole range between 30 and 90 %RH (Percentage Relative Humidity)y)

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.209-209
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• 2008

$BaTiO_3$는 대표적인 강유전체 재료로서 적층형 세라믹 콘덴서 (MLCC), PTC thermistor, resonator 등 다양한 분야에서 사용되고 있다. $BaTiO_3$ 기본조성으로 하는 PTC 써미스터는 온도가 올라감에 따라 저황이 높아지는 특성을 가지고 있으며, 이러한 PTCR 특성은 작동되는 큐리온도에 따라 그 적용이 달라진다. PTCR 소자는 소결온도, 소결분위기, 불순물, 첨가제 등의 제조공정상의 인자들과 기공률, 결정립 크기 등이 복합적으로 작용해 PTCR 특성에 영향을 미치기 때문에 제조하기에 무척 까다로운 소자로 알려져 있다. 하지만 우수한 특성을 지닌 PTCR 소자를 제조하기 위하여 새로운 조성개발이 이루어지고 있으며, 전기적 특성 개선, 재현성 확보, 제조원가 절감 등의 측면에서 새로운 공정개발이 이루어지고 있다. 본 연구에서는 Sm을 첨가한 $BaTiO_3$계 재료의 PTCR 특성에 미치는 Ti/Ba ratio 등의 변화에 따른 영향을 조사하고 공기 중과 환원분위기 중에서 소결된 시편의 차이점과 재산화 처리에 따른 PTC 특성에 미치는 영향을 R-T 측정으로 고찰하였다. 본 조성은 환원 분위기에서 소결할 경우 그 미세구조는 Ti/Ba ratio비가 높을 때 grain size가 커져 상온 비저항을 낮출 수 있었다. Sm 첨가로 상온 비저항값은 낮출 수 있었으나 공기 중에서 재산화 처리하더라도 jumping ratio$(R_{max}/R_{25^{\circ}C})$는 Ti/Ba ratio와 거의 무관한 것으로 분석되었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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• pp.402-410
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• 2000

As the combustion process of CWM consists of the water evaporation, the release and combustion of volatile matter, and the combustion of char for every particle, it is more complex than that of existent liquid fuel. Though the many studies on CWM combustion have been carried out by the single droplet using hanging methods or the multiple droplet using atomization methods, any report don't presents definite solution about the effects by the initial water evaporation and combustion of volatile. When CWM is suddenly exposed in the high temperature surroundings, the internal water evaporates and then each droplet builds up pores. Besides, porosity rate changes along the temperature of surroundings, the composition ratio of CWM, and the initial diameter of droplet. In result, because it affects the whole combustion rate, the combustion of CWM has complex mechanism as compared with the combustion of liquid or gas fuel. Therefore, concentrating on porous structure of CWM, this study has proceeded to acquire the basic data on the CWM injection combustion and closely examines the effects of the first stage combustion on the whole combustion by measuring the diameter variations, pore rate, mass fraction burned, and the internal temperature changes of CWM droplet. The results demonstrate that $60{\sim}70%$ of initial mass is reduced during water evaporation and volatile combustion period, and swelling rate, mass faction burned, and density variation are greatly concerned with atomization of CWM etc.

• Korean Journal of Agricultural Science
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• v.9 no.2
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• pp.453-460
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• 1982

In order to investigate the effect of $AgNO_3$ pretreatment on reducing $SO_2$ injury in leaves of Forsythia koreana, changes of pH, chlorophyll content, peroxidase activity, sulfur content, and stomatal behaviour in leaves were examined. 1. $AgNO_3$ sprayed at 200 ppm or above increased black spot development in lower epidermis of leaves. But pretreatment with 100 ppm $AgNO_3$ significantly reduced de foliation and visible injury rate of leaves exposed to $SO_2$. 2. $AgNO_3$ pretreatment prevented lowering pH and decreasing chlorophyll content induced by $SO_2$ injury in leaves. But both $AgNO_3$ pretreatment and $SO_2$ exposure increased peroxidase activity in leaves. 3. $AgNO_3$ pretreatment did not affect reducing $SO_2$ absorption and stomatal opening in leaves exposed to $SO_2$.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.75-75
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• 2010

3D 패키징 기술은 전기소자의 소형화, 고용량화, 저전력화, 높은 신뢰성등의 요구와 함께 그 중요성이 대두대고 있다. 이러한 3D 패키징의 연결방법은 와이어 본딩 또는 플립칩등의 기존의 방법에서 TSV(Through Silicon Via)를 이용하여 적층하는 방법이 주목받고 있다. TSV는 기존의 와이어 본딩과 비교하여 고집적도, 빠른 신호전달, 낮은 전력소비 등의 장점을 가지고 있어 많은 연구가 진행되고 있다. TSV의 세부 공정 중 비아필링(Via filling)기술은 I/O수 증가와 미세피치화에 따른 비아(Via) 직경의 감소 및 종횡비(Via Aspect Ratio)증가로 인해 기존 필링 공정으로는 한계가 있다. 기존의 비아 홀(Via hole)에 금속을 필링하기 위한 방법으로 전기도금법이 많이 사용되고 있으나, 전기도금법은 전기도금액 조성, 첨가제의 종류, 전류밀도, 전류모드 등에 따라 결과물에 큰 차이가 발생되어, 최적공정조건의 도출이 어렵다. 또한 20um이하의 비아직경과 높은 종횡비로 인하여 충진시 void형성등의 문제점이 발생하기도 한다. 본 연구에서는 용융솔더와 진공을 이용하여 비아를 필링시켰다. 이 방법은 관통된 비아가 형성된 웨이퍼 양단에 압력차를 주어, 작은 직경을 갖는 비아 홀의 표면장력을 극복하고, 용융상태의 솔더가 관통된 비아 홀 내부로 필링되는 방법이다. 관통 비아홀이 형성 된 웨이퍼 위에 솔더페이스트를 $250^{\circ}C$이상 온도를 가해 용융상태로 만든 후 웨이퍼 하부에 진공을 형성하여 필링하는 방법과 용융솔더를 노즐을 통하여 위쪽으로 유동시켜 그 위에 비아홀이 형성된 웨이퍼를 접촉하고 웨이퍼 상부에 진공을 형성하여 필링하는 방법으로 실험을 각각 실시하였다. 이 때, 웨이퍼 두께는 100um이하이며 홀 직경은 20, 30um, 웨이퍼 상부와 하부의 진공차는 약 0.02~0.08Mpa, 진공 유지시간은 1~3s로 실시하여 최적 조건을 고찰하였다. 각 조건에 따른 필링 후 단면을 전자현미경(FE-SEM)을 통해 관찰하였다. 실험 결과 0.04Mpa 이상에서 1s내의 시간에 모든 비아홀이 기공(Void)없이 완벽하게 필링되는 것을 관찰하였으며 이 결과는 기존의 방법에 비하여 공정시간을 감소시켜 생산성이 대폭 향상 될 수 있는 방법임을 확인하였다.

• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.110-116
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• 2005

Suitable compositions which are sinterable at low temperature in the $BaO-B_{2}O_{3}-ZnO$ glass system were investigated as a function of the ratio between BaO and ZnO. The effect of $Al_{2}O_3$ filler on densification and physical characteristics of the glass was also examined. When the amount of $Al_{2}O_3$ filler increased, the densification rate and the values of dielectric constant, thermal expansion coefficient and hardness in the glass-filler composites decreased gradually. The decreasing rate of the physical properties accelerated when fine $Al_{2}O_3$ filler was used. However, the fracture toughness of the composite rather increased due to the existence of filler particles and pores which effectively suppressed crack propagation with addition of fine $Al_{2}O_3$ filler.

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.225-230
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• 1988

The strength and thermal shock resistance of $Al_2O_3-ZrO_2$ composites have been studied. The tetragonal $ZrO_2$ powder containing 1 mol.% $Y_2O_3$ and monoclinic $ZrO_2$ powder were prepared by coprecipitation method and subsequently mixed with $Al_2O_3$ powder and granulated by sieving. Duplex composites were prepared by dry mixing matrix agglomerate with 15 to 30 vol.% of dispersion agglomerate, followed by pressing and sintering at 1$600^{\circ}C$ for1 hr. These $Al_2O_3-ZrO_2$ 2 composites having heterogeneous structure showed improved thermal shock behaviors because of the microcracking and pores in dispersed granules, and compressive stresses around dispersed granules resulting from $ZrO_2$ transformation.